Merge tag 'v3.53.0' into develop

always flushing atexit to fix #235 v3.53.0

# gpg: Signature made Wed Sep  9 13:19:08 2020 CEST
# gpg:                using RSA key 149325FD15904E9C4EB89E95E81444E9CE1F695D
# gpg: Good signature from "Rick van Hattem <wolph@wol.ph>" [ultimate]
# gpg:                 aka "[jpeg image of size 9662]" [ultimate]

Author: wolph